Answer
The largest peak will be the one corresponding to 1H-1H, and the smallest will be the one corresponding to 2H-2H.
Work Step by Step
From the atomic weight of hydrogen, 1.008, we know that the relative abundance of 2H is very small. Since the height of the peak corresponds to the relative abundance, the most common, and hence the one with the largest peak will be the one corresponding to 1H-1H. Likewise, the least common, and hence the one with the smallest peak will be the one that corresponds to 2H-2H.
